1. Field of the Art
This invention relates generally to endoscopes for use in medical fields, and more particularly to a synthetic resin casing of a manipulating head assembly of an endoscope, which is so arranged as to prevent twisting or rotational movements of a grip cover section of the casing.
2. Prior Art
Generally, medical endoscopes are largely constituted by a manipulating head assembly to be gripped by an operator for manipulation of various operation control means, an elongated insertion tube connected to and extended out on the front side of the manipulating head assembly, and a universal cable led out from a rear side of the manipulating head assembly to connect a light guide in the universal cable to a light source. At least an illumination window and an observation window are provided on a rigid tip end section at the fore distal end of the insertion tube. Illumination light is projected forward through the illumination window or windows to illuminate an intracavitary portion of interest during observation or examination through the observation window.
Since the manipulating head assembly is normally gripped and manipulated by one hand of an operator, it is formed of an electrically insulating material on its exterior surfaces and, for reduction of weight, housing in a casing of synthetic resin material. An angulation control mechanism is mounted in the casing of the manipulating head assembly for angularly bending an angle section which is provided at the fore end of the endoscopic insertion tube. In addition, a light guide or guides, signal cable, biopsy channel tube, air/water feed tube, angulation control wires are threaded through the manipulating head assembly of the endoscope. In order to support these internal components, a support plate and a tubular passage member, both of metal, are provided within the casing of the manipulating head assembly. The support plate is provided for supporting the angulation control mechanism and at the same time for guiding certain threaded member. The tubular passage member serves to enhance the shape retainability and strength of the manipulating head assembly. The support plate and the passage member are connected with each other. Normally, the passage member has a tubular body which is composed of a plural number of parts which are joined with each other by the use of screws or other fixation means.
Of the above-mentioned support plate and the tubular passage member which are accommodated within the casing of the manipulating head assembly of the endoscope, the support plate is required to have relatively high structural strength for supporting the angulation control mechanism. Therefore, the casing of the manipulating head assembly is arranged as a cover having an increased wall thickness at least in an angulation mechanism mount portion. On the other hand, the casing of the manipulating head assembly is not required to have high strength in particular from a grip portion to a fore end portion which is connected to the insertion tube. Therefore, the grip portion of the casing is usually reduced in wall thickness to cut the total weight of the casing. Further, a divisional cover section with an entrance to the biopsy channel is provided between a grip cover section and a main cover section. A manipulating head assembly with these casing arrangements is well known in the art, for example, from Japanese Patent Publication H5-3287.
In this connection, the manipulating head assembly is gripped by an operator at the grip cover section which is formed of thin wall synthetic resin material, so that twisting forces are applied to the grip cover section of the casing during use. Therefore, the casing of the manipulating head assembly is usually provided with an anti-twist mechanism for preventing deformations of the grip cover section by rotational twisting forces. In the case of the prior art mentioned above, an anti-twist mechanism for the grip cover section is constituted by a metallic reinforcing member provided internally of the grip cover section, and a link member provided for connection to a reinforcing tube provided internally of the divisional cover section and having a flat surface on a lateral side face to face with and in small gap relation with a flat surface on a lateral inner surface of the grip cover section of the casing. When a twisting force is applied to the grip cover section, the two flat surfaces are brought into abutting engagement with each other to prevent rotational movements of the grip cover section.
The grip cover anti-twist mechanism by the above-mentioned prior art however still has a number of problems. Namely, restrictions are imposed on the inner and outer surfaces of the grip cover section and the link member. Particularly in a case where the grip section of the casing is formed approximately in a circular shape in section, a difficult machining operation is required to provide a flat surface on the inner side of the grip cover section, and the weight of the manipulating head assembly is inevitably increased for this reason. Besides, difficulties are encountered in directly connecting the reinforcing member, which is provided across the main cover section and the grip cover section of the casing, to the reinforcing tube which is provided internally of the divisional cover section. In addition to an increased number of parts, the use of the link member results in a restriction on the available internal space of the manipulating head assembly.